A variety of apparatus are known for the wet development of photosensitive material They are generally designed such that photosensitive material is carried into a processing tank filled with processing solution, more specifically developing solution The photosensitive material is developed while it is immersed in the solution for a predetermined time. It is often desired to continuously develop webs or sheets of photosensitive material with such processing apparatus. The tank is often of the open type which keeps the surface of processing solution open to the ambient. Upon contact with air, the processing solution not only evaporates, but also undergoes a temperature lowering as well as deterioration and changes of properties such as oxidation by taking in oxygen from air and a pH lowering by taking in carbon dioxide from air.
Many problems arise from evaporation of the processing solution. Evaporation would create a difference in concentration of the processing solution between the top and the bottom of the tank, adversely affecting uniform development. An extra volume of processing solution must be replenished since the processing solution decreases its volume rather quickly. In addition, vapor of processing solution will deposit on nearby parts of the processing apparatus, particularly on rollers for conveying photosensitive material and dry to a tacky-dry state, causing sticking and stains.
It is apparent that deterioration and property changes of the processing solution adversely affect development.
For optimum development, the processing solution should be maintained at an appropriate temperature in the range of 20.degree. to 60.degree. C. A larger amount of heating energy is necessary to maintain the solution at the temperature if a larger amount of heat dissipates from the solution surface.
When the photosensitive material processing apparatus having an open top processing tank is applied to a processing section of a silver salt photographic copying machine, selection of installation conditions and a photosensitive material transfer path is limited. More particularly, the processing tank must be placed with its open top faced vertically upward so as to prevent the solution from spilling. It is necessary to carry photosensitive material into and out of the processing tank through its open top portion. Consequently, the path along which the photosensitive material is passed through the tank is limited to some patterns The design of the processing tank must be made within a limited range of freedom in consideration of proper orientation. Also a relatively large space is necessary for installation of the tank and accessories, resulting in a larger size of apparatus.
These problems are aggravated when a plurality of tanks are arranged in juxtaposition. Such is often the case in an automatic photosensitive material processing apparatus in which a series of tanks are arranged for development, bleach-fixation, and washing and an exposed photosensitive material is passed through the successive tanks for development.